The American Quarterly Review, No. 17, March 1831

by Various

"Although all these formations have been deposited by water, and although they may all be found in the same locality lying upon each other, the passage from the one to the other is never made by insensible gradations. A sudden and marked change is always to be perceived in the physical nature of the deposit, and in that of the organized beings whose remains are found in it. Thus it is evident, that between the epoch at which the limestone of Jura was deposited, and that of the precipitation of the system of greensand and chalk which covers it, there has been upon the surface of the globe a complete change in the state of things. The same may be said of the epoch that separates the precipitation of the chalk from that of the tertiary formations; as it is also evident that in every place the state or nature of the liquid, whence the earths were precipitated, must have changed completely between the time of the formation of the tertiary strata, and that of the diluvium.

"These considerable variations, sudden, and not gradual, in the nature of the successive deposits formed by the waters, are considered by geologists as the effects of what they call 'The Revolutions of the Globe.' And even although it is very difficult to say exactly in what these revolutions consisted, their occurrence is not the less certain on that account.

"I have spoken of the chronological order in which these different sedimentary strata have been deposited: I must therefore state that this order has been determined by following, without interruption, each different formation, to those regions in which it could be ascertained beyond question, and over a great horizontal space, that some particular layer was above some other. Natural excavations, such as the cliffs that border the sea, common wells, and Artesian fountains, with the excavation of canals, have furnished powerful aid in this inquiry.

"I have already remarked, that all these sedimentary formations are stratified. In level countries, as might be expected, the disposition of the layers is nearly horizontal. In approaching mountainous countries, this horizontality, generally speaking, ceases; finally, on the sides of mountains, some of these layers are very much inclined; they even sometimes attain a vertical direction.

"May not the inclined deposits that we see upon the slopes of mountains, have been deposited in inclined or vertical positions? Or is it not more natural to suppose, that they originally formed horizontal beds, like the contemporaneous beds of the same nature with which the plains are covered, and that they have been lifted up and assumed new directions at the moment of the elevation of the mountains on whose sides they rest?

"As a general principle, it does not appear impossible that the crests of mountains may have been incrusted in place, and in their actual position, by sedimentary deposits, since we daily see the vertical sides of vessels, in which waters charged with sulphate of lime evaporate, covered with a saline crust, whose thickness is continually augmented; but the question before us does not present this general aspect, for it is merely required to determine whether the known sedimentary formations can have been thus deposited. To this question we must reply in the negative, as can be shown by two species of considerations, wholly different from each other.

"Incontestable geological observations have shown, that the calcareous layers which constitute the summits of Buet in Savoy, and Mount Perden in the Pyrenees, elevated 11,000 or 12,000 feet above the level of the sea, have been formed at the same time with the chalk of the cliffs that border the British channel. If the mass of water whence these strata were precipitated had risen 11,000 or 12,000 feet, the whole of France would have been covered, and analogous deposits must have existed upon all heights not exceeding 9,000 or 10,000 feet; now, it is found, on the contrary, that in the north of France, where these deposits appear to have undergone little change, the chalk never reaches a height of more than 600 feet above the level of the present sea. They present precisely the disposition of a deposit formed in a basin filled with a liquid whose level has never reached any points that are at the present day elevated more than 600 feet.

"I pass to the second proof, borrowed from Saussure, and which appears even more convincing.

"Sedimentary formations often contain pebbles rounded by attrition, and of a figure more or less elliptical. In the places where the stratification is horizontal, the longer axes of these pebbles are all horizontal, for the same reason that an egg cannot stand upon its point. But where the strata are inclined at an angle of 45°, the greater axes of many of these pebbles form this same angle with the horizon; and when the layers become vertical, the greater axes of many of the pebbles become vertical also.

"This observation, in respect to the position of the axes of the pebbles, demonstrates, that the sedimentary formations have not been deposited in the position they now occupy; they have been raised in a greater or less degree, when the mountains, whose sides they cover, have arisen from the bosom of the earth.